An ejector or venturi may be used as a vacuum source in dual path purging systems in an engine for fuel vapor recovery. For example, an inlet of an ejector may be coupled to an engine intake upstream of a compressor via a hose or duct and an outlet of the ejector may be coupled to an intake of the engine downstream of the compressor via a hose or other conduit. Motive fluid through the ejector provides a vacuum at an ejector suction inlet which may be coupled to a fuel vapor canister to assist in purging the fuel vapor canister during boosted operation.
In some examples, the motive fluid may contain fuel vapors, untreated engine emissions, and/or engine crankcase vapors. If the ejector develops a leak or if one or more hoses or ducting coupled to the ejector becomes degraded, it may be possible for gases to escape to the atmosphere. For example, leaks may be manifested at the inlets of the ejector or at the outlet of the ejector, e.g., when the ejector is stressed causing breakage or degradation in the body of the ejector device. As another example, leaks may be manifested when hoses, conduits, or ducting coupled to the inlets or outlet of the ejector degrade, break, or decouple from the ejector.
Some approaches diagnose and detect leaks in ejector system components adjacent to the ejector inlets and/or upstream of the ejector inlets. For example, using a variety of sensors in an engine system, leaks may be detected in hoses, conduits, or ductwork coupled to the inlet of the ejector or at other locations in an ejector system upstream of the ejector outlet. However, such approaches fail to diagnose or detect leaks in an ejector system at or downstream of the ejector outlet. For example, a hose or other ducting may be used to couple the outlet of an ejector to an engine intake at a position upstream of a compressor. If such a hose degrades, or decouples from the ejector outlet, the resulting leak in the ejector system may remain undetected leading to increased emissions and degradation in engine operation.
The inventors herein have recognized the above-mentioned disadvantages and have developed a dual path purge system for an engine. In one example approach, a multi-path purge system, (such as a dual-path system) for an engine comprises: an ejector including a restriction, first and second inlets, and an outlet, and a shut-off valve hard-mounted to an intake of the engine and coupled to the outlet. For example, the shut-off valve may be configured to close in response to a disconnection of the shut-off valve with the intake of the engine.
In this way, the shut-off valve coupled to the ejector outlet may be closed in response to a detected leak or other degradation in the multi-path purge system in order to reduce unwanted emissions due to leaks in a tube coupling the ejector outlet to the engine intake. For example, in response to a detected disconnection between the shut-off valve and the intake of the engine, functioning of the evaporative emissions system may be discontinued and mitigating actions may be performed so that unwanted emissions may be reduced. Specifically, the approach may reduce the need to monitor all sections of a purge system to diagnose leaks. Further, the approach may reduce a number of sensors required to monitor a purge system for leaks. Further still, purge system leaks may be determined without adding any additional sensors to the vehicle system.
The above advantages and other advantages, and features of the present description will be readily apparent from the following Detailed Description when taken alone or in connection with the accompanying drawings.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.